C ++将数组中的数字重新排列为升序

Posted 2023-03-25

【中文标题】C ++将数组中的数字重新排列为升序

【英文标题】：C++ Rearranging numbers in an array into ascending order

【发布时间】：2021-11-07 19:46:33

【问题描述】：

所以我有一个 C++ 实验室，需要我打印出一个数组，删除一些数字，然后插入一些数字。我设法删除了正确的数字，然后在末尾插入数字，但我需要将数组按升序排序，例如：1、2、3、4。我认为这将是容易的部分，但它给我带来的麻烦比我想象的要多。我尝试使用带有嵌套 if 循环的 for 循环，该循环适用于普通数组，但我想在混合中涉及指针让我很难过。当前代码运行并执行除排序之外的所有操作。任何提示或帮助表示赞赏。代码和输出发布在下面。 This is an image of the assignment description

#include <iostream>
using namespace std;
class Array //The array class

private:
     //Data members capacity, size, arr (a pointer that points to the first element of the array in the heap)v and two functions to move integers in the array.
     int capacity;
     int size;
     int* arr;
     void moveTowardFront(int index);
     void moveTowardEnd(int index);
public:
     Array(int capacity);//parameter
     ~Array();//destructor
     //two member function declarations 
     void insert(int num);
     void print() const;
     void remove(int num);

;
//insert method
void Array::insert(int num)

     
          //if size is 0, then move number taken from insert call into the first element of the array and increment size before returning
          if (size == 0)
          
               arr[0] = num;
               size++;
               return;
          
          int index = 0;
          while (&num < &arr[index] && index < size) //while the address of the number taken from insert function call is less than the address of the element [index] in the arr array
                                                 //and the index is less than the size of the array 
          
               index++; //then we increment the index
          
          moveTowardEnd(index); //move value of element toward the end 
          //after the while loop we move the value of the number taken from main insert call into the arr element [index] after it has been incremented so we don't overwrite values 
          arr[index] = num;
          size++;
          //then we increment the size of the array because a new value has been inserted 
     


// Delete member function
void Array::remove(int num)

     int index = 0; //start index at 0
     //while number from main is not equal to the array element of index and the index is smaller than the size, we increment the index
     while (num != arr[index] && index < size)
     
          index++;
     
     //if index is equal to the size then output the number from main and say it isn't on the list so no removal
     if (index == size)
     
          cout << num << " is not in the list. ";
          cout << "No removal." << endl;
          return;
     
     //move toward front function call on index value and post-increment. Then post-decrement size 
     moveTowardFront(index++);
     size--;


//print method
void Array::print() const

     //rearrange the digits in ascending order 
     for (int i = 0; i < size; i++)
     
          //print out values based on value of size taken from insert method 
          cout << *(arr+i) << " "; //arr points to first element in heap and then moves over by i to the next element for each iteration 
     



// Helper function to move the elements of array towards end
void Array::moveTowardEnd(int index)

     int* temp = &arr[index];
     int* temp2 = &arr[size-1];
     arr[index] = *temp2;
     arr[size] = *temp;
     return;

// Helper function to move the elements of array towards front
void Array::moveTowardFront(int index)

     int* temp = &arr[index];
     int* temp2 = &arr[size-1];
     arr[index] = *temp2;
     arr[size] = *temp;
     return;


//Destructor to clean up by deleting the space allocated 
Array::~Array()

     delete[]arr;


//Parameter constructor to allocate space 
Array::Array(int cap)
     :capacity(cap)

     //move space allocated by array with capacity being taken from main into the arr pointer so pointer can point to first element in heap 
     arr =  new int[capacity]  ;//allocating memory with the new operator
     size = 0;//initialize size to 0



int main()

     // Declaration of any array of capacity 20
     Array array(20);
     // Inserting some elements and printing array
     array.insert(15);
     array.insert(13);
     array.insert(10);
     array.insert(14);
     array.insert(11);
     array.insert(17);
     array.insert(14);
     cout << "Printing array after insertions: " << endl;
     array.print();
     cout << endl;
     // Removing two elements and printing array
     array.remove(13);
     array.remove(11);
     cout << "Printing array after removals: " << endl;
     array.print();
     cout << endl;
     // Inserting two more elements and printing array
     array.insert(8);
     array.insert(22);
     cout << "Printing array after more insertion" << endl;
     array.print();
     cout << endl;
     // Try to remove an element, which is not in the array
     array.remove(31);
     return 0;

【问题讨论】：

我会冒险出去，猜你不能调用std::sort？但这归结为两个问题之一 - 您必须对底层数组进行排序，这与所有这些代码没有任何关系，或者您必须处理其他问题，例如内存管理错误。

【参考方案1】：

有很多方法可以对数组进行排序。常用的是被称为快速排序的算法：https://en.wikipedia.org/wiki/Quicksort

取自***页面的伪代码：

algorithm quicksort(A, lo, hi) is
    // first we check if the lo and hi
    // are natural numbers (without this check, you
    // will get an overflow error because, at some point
    // the program will access something like A[-1]
    // which does not exists !
    if lo >= 0 && hi >= 0 then
         // if the indexes are in correct order, continue
         if lo < hi then
              // we find the index of the pivot and... 
              p := partition(A, lo, hi)
              // ...apply quicksort for the left side and the
              // right side of the array
              quicksort(A, lo, p - 1)
              quicksort(A, p + 1, hi)

algorithm partition(A, lo, hi) is
    // we set the pivot value to the
    // final value of the array 
    pivot := A[hi]
    // we set the pivotIndex (i) to
    // the start of the array
    // ! NOTICE that A[i] != pivot
    // aka. A[pivotIndex] != pivotValue
    i := lo - 1
    // we traverse the array from the start
    // to the end (inclusive) aka. we traverse
    // the array in this interval: [lo, hi]
    for j := lo to hi do
        // if the current element is
        // less than the value of the pivot
        // (or equal to it), then increment the i
        // and swap it with the element at i (pivotIndex)
        // ! NOTICE that j is automatically incremented 
        if A[j] <= pivot then
            i := i + 1
            swap A[i] with A[j]
    return i

您必须自己将伪代码翻译成 C++。他们似乎使用名称 algorithm 来表示函数定义，并使用 := 运算符来进行赋值，但除此之外它与 C++ 语法并没有太大不同。他们在一个地方写了swap A[i] with A[j]，你可能看起来更像：

int temp = A[i];
A[i] = A[j];
A[j] = temp;